In Feb 2006 we invited Savannah projects admins to the savannah-announce
mailing list.

We didn't tried to invite 40,000 users because this is a bit much for
Mailman and the mail system to handle; so we invited the \~3000 admins.

The preferred way to invite people is to use the web interface - there's
no command-line equivalent, and previous attempt to recreate one ended
up sending invites that did not allow users to actually subscribe. So we
split the admins list and sent invites using 2x200 batches, and not all
in a row to avoid being marked as spammers (we're, still, mass-mailing
with a non-negligeable percentage of dead ones).